The formation of dentin by odontoblast involves the initial deposition of an uncalcified matrix, predentin that is transformed to dentin several microns from the cell borders. The biochemical mechanisms involved in this process are unknown, but certain data suggest that noncollagenous proteins (NCPs) and proteoglycans (PGs) are involved. The aim of these investigations is to elucidate the nature, metabolism and biological significance of NCPs and PGs of rat dentin in order to ascertain the role they might play in dentinogenesis. In recent studies from this laboratory we have employed improved techniques to isolate these macromolecules with procedures designed to eliminate proteolytic degradation and losses. These studies have shown that rat dentin contains phosphoproteins, two pools of PGs, acidic glycoproteins, serum proteins and Gamma-carboxyglutamate (G1a)- containing proteins. Each class of macromolecules is being further characterized biochemically. An improved odontoblast organ culture system is being used to study the biosynthesis of the NCPs and PGs. These studies are designed to advance our knowledge about the basic mechanisms involved in the formation of teeth and bones.